Feathers have a variety of functions: flight, temperature regulation, protection against environmental and climatic extremes, and courtship displays (colorful feathers, selective erection of certain feathers, etc). Without feathers, wild birds could not survive. Therefore, careful and regular attention to the feathers and their condition is vital. The process by which a bird grooms itself is called “preening.’ It will use its beak to condition and waterproof its feathers and to meticulously remove the sheaths through which all new contour and flight feathers emerge. Birds use their feet and claws to perform this latter function on contour feathers located on the head. Further, it is not uncommon for birds to rub against various objects in their immediate environment to perform this function. Mutual preening is common among cage mates. Normal preening behavior must be distinguished from feather picking and feather mutilation.